Journal Article

HvPIP1;6, a Barley (<i>Hordeum vulgare</i> L.) Plasma Membrane Water Channel Particularly Expressed in Growing Compared with Non-Growing Leaf Tissues

Wenxue Wei, Erik Alexandersson, Dortje Golldack, Anthony John Miller, Per Ola Kjellbom and Wieland Fricke

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 8, pages 1132-1147
Published in print August 2007 | ISSN: 0032-0781
Published online August 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm083
HvPIP1;6, a Barley (Hordeum vulgare L.) Plasma Membrane Water Channel Particularly Expressed in Growing Compared with Non-Growing Leaf Tissues

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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The aim of the present study was to identify water channel(s) which are expressed specifically in the growth zone of grass leaves and may facilitate growth-associated water uptake into cells. Previously, a gene had been described (HvEmip) which encodes a membrane intrinsic protein (MIP) and which is particularly expressed in the base 1 cm of barley primary leaves. The functionality of the encoding protein was not known. In the present study on leaf 3 of barley (Hordeum vulgare L.), a clone was isolated, termed HvPIP1;6, which has 99% amino acid sequence identity to HvEmip and belongs to the family of plasma membrane intrinsic proteins (PIPs). Expression of HvPIP1;6 was highest in the elongation zone, where it accounted for >85% of expression of known barley PIP1s. Within the elongation zone, faster grower regions showed higher expression than slower growing regions. Expression of HvPIP1;6 was confined to the epidermis, with some expression in neighboring mesophyll cells. Expression of HvPIP1;6 in Xenopus laevis oocytes increased osmotic water permeability 4- to 6-fold. Water channel activity was inhibited by pre-incubation of oocytes with 50 μM HgCl2 and increased following incubation with the phosphatase inhibitor okadaic acid or the plant hormone ABA. Plasma membrane preparations were analyzed by Western blots using an antibody that recognized PIP1s. Levels of PIP1s were highest in the elongation and adjacent non-elongation zone. The developmental expression profile of HvPIP2;1, the only known barley water channel belonging to the PIP2 subgroup, was opposite to that of HvPIP1;6.

Keywords: Barley (Hordeum vulgare L.); Cell elongation zone; Epidermis; Leaf growth; Membrane intrinsic proteins; Plasma membrane water channel

Journal Article.  10729 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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